The Go-To Revolution

Books on amateur astronomy used to supply only two important pieces of advice about tripods and mounts.
First: Don’t cheap out. Invest in something sturdy and steady.
Second: Choose between an altazimuth mount and an equatorial mount. The simple altazimuth mount is adjustable on two axes: up and down (altitude) and left and right (movement parallel to the horizon, or azimuth). There is nothing automatic about most altazimuth mounts. If you are trying to follow an object, you must continually adjust both the altitude and the azimuth. The alternative equatorial mount is aligned with the earth’s rotational axis and, therefore, may be made to follow a celestial object by adjusting one axis only (to counteract the rotation of the earth).

These two pieces of advice used to be quite sufficient. In the late 1990s, however, popular manufactures started selling even some entry-level telescopes with go-to computer controllers that drive servo-motors built into the telescope mount. The handheld go-to controller stores a database of the locations of thousands of celestial objects. Select a object or punch it its coordinates, and (if properly trained and aligned) the telescope’s servos will point the telescope at your target object.

In addition to servo motors for go-to capability, equatorial and altazimuth mounts typically include a clock drive that synchronizes the telescope with the earth’s rotation so that a given object can be followed—“tracked”—without your having continually to re-aim the telescope.
Go-to capability can work on telescopes that have either altazimuth or equatorial mounts. For example, the go-to features on the Meade ETX 90EC telescope can be used in either equatorial or altazimuth mode. One just has to be careful that the computer has been informed of your choice (usually accomplished on the setup menu). The amazing thing is that go-to technology has become sufficiently affordable to be included in even entry-level telescopes. This feature has truly revolutionized amateur astronomy, greatly broadening its appeal. Keep in mind that the “go-to” hand paddle must typically be purchased as an accessory, and will cost several hundred dollars itself. If this capability is important to you, you should buy a telescope that can be updated at a later time.